MDMA:
effects- very very very euphoric (extreme happiness), loads of love, your body feels perfect but not always energetic. its mainly about the happy. you can usually sleep on MDMA
dangers: not many, it is the third safest popular drug in britain, coming before alcohol, cannabis, nicotine, valium etc
amphetamine:
effects- energy and restlessness, happiness and well being but no heavenly bliss, want to walk and move, does not let you sleep, messiness and such, mainly about the tweaky energy
dangers- can give you stimulant psychosis, keeps you up, comedown, is very addictive (physically and mentally), tolerance skyrockets quickly, damages neurotransmitter receptors for dopamine (and possibly serotonin) the list is endless...
methamphetamine (crystal meth):
effects- like regular amphetamine but much stronger, for longer, more happiness, mainly about the hardcore speeding, tweaking
dangers- very toxic, much more addictive, can keep you up for well over a week, everything regular amphetamine has and more
so MDMA is very lovey and happy and relatively safer, the other two are about energy and tweakiness and some happy aswell. the difference is so obvious to me but when i try and explain it, MDMA and amphetamine sound pretty similar in effects which they aren't really. you just need to know the roles each characteristic plays. like in MDMA the main thing is love, happiness, bliss, like floating on a cloud style of thing. for speed (both kinds) its about the energy, fastness, chattiness and the happiness that comes from those.